Several works have investigated the impact of urbanisation on carabid activity density using urban-rural gradients. Such works compared activity density recorded from green spaces located in different parts of a city and assigned to categories of increasing urban intensity, which poses two problems: (1) since the gradient is divided into categories, it is impossible to model continuous variations in biotic responses, and (2) sites representative of different urbanisation levels are not true segments of the same ecological continuum. To surpass these problems, we modelled variations in carabid activity density along an urban-rural transect within a single green space extending from the city centre of Rome to rural environments. Carabids were sampled by pitfall traps from sites distributed along the entire gradient. We used breakpoint regressions to model how (1) carabid activity density, (2) carabids/beetles ratio, (3) carabids/insects ratio and (3) carabids/arthropods ratio varied along the gradient. As already observed for various organisms in urban environments, we found that activity density of carabids and their contribution to the abundance of beetles, insects and arthropods, peaked in the middle of the gradient. This supports the intermediate disturbance hypothesis, according to which moderate urbanisation may favour diversity by increasing habitat heterogeneity.

The Italian fauna includes about 170 species/subspecies of dung beetles, being one of the richest in Europe. We used data on dung beetle distribution in the Italian regions to investigate some macroecological patterns. Specifically, we tested if species richness decreased southward (peninsula effect) or northward (latitudinal gradient). We also considered the effects of area (i.e., the species–area relationship), topographic complexity, and climate in explaining dung beetle richness. Finally, we used multivariate techniques to identify biotic relationships between regions. We found no support for the peninsula effect, whereas scarabaeines followed a latitudinal gradient, thus supporting a possible role of southern areas as Pleistocene refuges for this group of mainly thermophilic beetles. By contrast, aphodiines were more associated with cold and humid climates and do not show a distinct latitudinal pattern. In general, species richness was influenced by area, with the Sardinian fauna being however strongly impoverished because of its isolation. Faunal patterns for mainland regions reflect the influence of current ecological settings and historical factors (Pleistocene glaciations) in determining species distributions.

As concrete jungles, urban areas may be considered extreme environments for most animal groups. Yet, cities host unexpected high values of biodiversity, sometimes also in the most urbanized sectors. Several works have investigated the impact of urbanization on carabids using urban-rural gradients. However, most research has been done in north-western and central Europe, whereas urban communities in the Mediterranean region remain largely unexplored. Also, due to the high fragmentation of green spaces in urban areas, studies on the urban-rural gradient typically used data collected from several green spaces along the gradient, not from a single large area, which complicates interpretation because of the many confounding factors associated with inter-site variability. Aim of this research was to investigate the response of carabid populations to urbanization by analysing how their activity density varied along an urban-rural gradient within a single, large green space. The study was conducted in Rome (Italy), in the Appia Antica Regional Park, an urban park of 3,500 ha, which extends for some 16 km from the city centre to the rural environments out of the city. Carabids were sampled by pitfall traps from nine sites along the entire urban-rural gradient. We calculated the total carabid activity density, number of carabids/total Coleoptera (CAR/COL), and number of carabids/total insects (CAR/INS). As already observed for various organisms in urban environments, we found that carabid acitivity density peacked in the middle of the gradient, where it was more than six times higher than in the city centre and about three time higher than in the rural sites. This supports the intermediate disturbance hypothesis, according to which moderate urbanization may favour diversity by increasing habitat heterogeneity. CAR/COL and CAR/INS also peacked in the middle of the gradient, which indicates that carabids are the insect taxon most favoured by intermediate urbanization.

The myrmecophilous carabid beetle, Paussus favieri, has a circum-Mediterranean distribution and it is completely dependent upon its host ant Pheidole pallidula during all stages of its life history. Using molecular sequence data we inferred the phylogenies of the populations of both the beetle and its ant host to determine if there are signs of co-evolution. A total of 34 P. favieri from France, Spain, Portugal, Morocco and Tunisia and 42 Ph. pallidula workers from the same countries, plus Greece and Italy, were collected and analyzed. Many mitochondrial and nuclear markers were sequenced, but only COI was evolving fast enough to infer the population-level phylogenies of the beetles and the ants. Preliminary analyses suggest that the European populations of P. favieri are derived from a single dispersal event from Africa, while several dispersal events are suggested for Ph. pallidula. We found the topologies of host and parasite trees to be generally congruent, as would be expected if the host and parasite have had a history of co-evolution or co-divergence.